How can I test End-to-end encryption

I have a nextcloud 13b4 instance with installed and activated end2end encryption. But none of the clients are allowing me to crypt a folder. What am I missing?

iOS client is 2.19.1 and android 2.0.0

On the desktop client, you still have to build it on your own. I asked for an update regarding the E2E implementation from the developers: